In charting the history of rigid gas permeable (RGP) contact lenses (CL), ,. it is evident that the emergence of today's materials is the result of CL designers striving to develop a more symbiotic relationship between the cornea and the CL. With higher gas permeable materials combined with knowledge gained from the PMMA era of lens modification, this symbiotic relationship becomes a reality. One such modification aiding this relationship is blending. Blending is perhaps the single most common RGP modification performed by the private practitioner. Presently, there is controversy among practitioners as to what blending actually does to the lens -- does it remove stock material or simply displace it? The effects of blending on two common RGP materials, Boston IV and Polycon II, were studied. The lenses were divided into an experimental and a control group and then weighed. A "B" (.2) blend was given to the experimental lenses and they were then re-weighed. This revealed (at the p = 0.0001 level for Polycon II and p = 0.003 for Boston IV) that blending of Boston IV and Polycon II lenses does remove material.
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